In mice, the mylk1 gene is a large gene spanning ~250 kb and comprising at least 31 exons. It encodes at least four protein products: two isoforms of the 220 kDa MLCK (also known as endothelial, long, or nonmuscle MLCK), a 130 kDa MLCK (also known as short or smooth muscle MLCK), and telokin (also known as kinase-related protein). Transcripts encoding these products are derived from four independent promoters within the gene. Each of the promoters within the mylk1 gene exhibits cell-specific differences in their activity [PMID: 16774989]. Both 130 kDa and 220 kDa MLCK contain a kinase (catalytic) domain, while telokin does not have a kinase domain.